21871780 has 24 divisors (see below), whose sum is σ = 52492608. Its totient is φ = 7498848.

The previous prime is 21871777. The next prime is 21871783. The reversal of 21871780 is 8717812.

It is an interprime number because it is at equal distance from previous prime (21871777) and next prime (21871783).

It is not an unprimeable number, because it can be changed into a prime (21871783) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 77974 + ... + 78253.

It is an arithmetic number, because the mean of its divisors is an integer number (2187192).

Almost surely, 2^21871780 is an apocalyptic number.

21871780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21871780 is an abundant number, since it is smaller than the sum of its proper divisors (30620828).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21871780 is a wasteful number, since it uses less digits than its factorization.

21871780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 156243 (or 156241 counting only the distinct ones).

The product of its (nonzero) digits is 6272, while the sum is 34.

The square root of 21871780 is about 4676.7274883192. The cubic root of 21871780 is about 279.6585122626.

The spelling of 21871780 in words is "twenty-one million, eight hundred seventy-one thousand, seven hundred eighty".